Investigation of the behaviour of selected ultrasonic guided wave modes to inspect rails for long-range testing and monitoring

Long-range ultrasonic testing (LRUT) uses guided waves in the kilohertz range to inspect many metres of an elongated component from a single point of access. This has considerable advantages for the rapid testing of long lengths for the detection of potentially harmful defects. This technique is well developed for structures that have a simple geometry, such as plates, rods, and pipes. However, this is a relatively new technology and there is still much to learn about the behaviour of guided waves and their application in complex structures, such as railway rails. The aim of this work was to identify suitable ultrasonic-guided wave modes that can detect common types of defects in each part of a rail (i.e. the head, web, and foot). The investigation was carried out using finite-element analysis and was validated experimentally. The findings of this research demonstrated the ability to detect transverse defects as small as 2 mm and 5 mm in the head and foot, respectively.